3rd generation (3G) systems, such as the Universal Mobile Telecommunication System (UMTS) have been developed and deployed to further enhance the communication services provided to mobile users compared to those communication services provided by the 2nd generation (2G) communication system known as the Global System for Mobile communication (GSM). In such 3G systems two distinct switch domains or networks have been identified for Radio Access Networks (RANs) which communicate with the mobile devices. These domains are the circuit switched (CS) domain and the packet switched (PS) domain. In the CS domain signals are physically routed to the appropriate destination through a unique connection whereas in the PS domain message packets are routed to the appropriate destination based on addresses in the packet. So for example, a UMTS CS domain is a UMTS RAN (known as UTRAN) communicating via a CS network and a UMTS PS domain is a UTRAN communicating via a PS network. In UMTS, the base stations which are part of the UTRAN are known as Node Bs and a mobile terminal is known as User Equipment (UE).
Other IP-based communication systems, such as wireless LAN (WLAN), Worldwide interoperability for Microwave Access (Wi-MAX), Wi-Fi, Long Term Evolution (LTE) systems, provide communication via a PS domain. It will be appreciated that a GSM system comprising a General Packet Radio System (GPRS) network includes a PS domain through the GPRS network.
With an increase in the number of wireless communication systems deployed and with the development of UEs having multi-mode capability (i.e. CS domain and PS domain), situations arise where a mobile device may be able to communicate via a PS domain or a CS domain or simultaneously via a PS domain and a CS domain. For example, to originate or receive a voice call or to continue a voice call which is already established in a particular coverage area, a mobile device may have the option to use a GSM CS domain or a GSM PS domain or a UMTS PS domain or a Wireless Local Area Network (WLAN) PS domain in that coverage area.
In the case when a voice call is already established, Voice Call Continuity (VCC) requires a voice call to be maintained when the voice call is handed over between different domains or different communication systems and between base stations in the same system. Handling call handovers within the same RAN is relatively easy. Handling call handovers or call establishment between different communication systems with different RANs and between different domains, each of which may involve completely different service providers, is more complicated and this is being addressed and standardised within the third Generation Partnership Project (3GPP).
The current approach defined in the 3GPP standards (3GPP TS 23.206 and TS 24.206) requires a mobile device to select a RAN and domain for call establishment and for call transfer decisions for implementing VCC based on the radio signal strength/quality of the RANs available to the mobile device and on a set of predefined operator VCC rules or policies. These operator policies are typically configured into the mobile device during initial provisioning and may be changed at a later time, for example, by over the air (OTA) provisioning, as the network VCC capabilities evolve.
As stated above, the VCC mobility approach currently defined in the 3GPP standards by which an appropriate RAN and domain are selected requires the mobile device to be the decision maker and to determine the events which trigger a decision. Other than the received signal strengths that are monitored by the mobile device and the predefined operator VCC rules or policies, the mobile device has no visibility into the overall network characteristics and thus, does not make selection decisions based on network resource related parameters, such as load-balancing, available bandwidth or Quality of Service (QoS) thresholds for triggering a decision. Thus, the current approach does not allow for a selection mechanism which is flexible enough to be controlled in real-time so as to take account of real-time network resource issues. For example, in a situation when a particular RAN and domain are specified in the predefined operator VCC rules and are available to the mobile device (as determined from monitoring the signal strengths from the RAN) but the domain is overloaded, a call will not be established or if a call is already established, the call will be terminated even though another domain and RAN may be available to the mobile device.
U.S. Pat. No. 6,567,667 discloses a domain selecting system which enables the network to tell the mobile device which services (e.g. services such as voice calls) are supported and/or preferred over which domains. The mobile device can then use this information to influence its decision as to which domain to use when initiating a particular service. For example, the network sends domain preference information for the services to the mobile device when the mobile device connects to a particular RAN. This patent is aimed at supporting migration of services from one domain to another and thus, although discloses sending network specified information such as mapping of certain services and applications to certain domains, or routing certain percentages of calls to one domain or routing calls to a domain that offers the lowest cost, this patent does not disclose the domain selection decisions being based on real-time network resource information. Nor does it address changing domains during an established call. Thus, the result for the specific situation described above would be the same for the system disclosed in this patent.
PCT patent application no. WO 2007/079582 describes a system for selecting a domain in a network for directing an incoming call to the mobile device. Domain selection policies or rules are stored in a network server and may be modified by the mobile device. User preferences are uploaded to the network with operator policies normally overriding user preferences. The domain selection policies are used by the network to select a domain for directing an incoming call to the mobile device.
There is therefore a need for an improved process for updating domain selection information which is flexible and takes account of information provided by the mobile device and network resource information.